The infection or transfection of cells by infectious viruses or retroviruses has been known for many years. Many methods for improving the rate of transfection have been used. Calcium chloride treatment of the cells has been used to allow naked DNA to pass through the cellular membrane. Improved vectors have been developed for increasing the level of infection. The use of lipids or liposomes to deliver the genetic material have also been used with some amount of success.
Particle mediated delivery has been used to transform numerous types of cells with a gold microparticle mediated delivery of DNA. The technique has been described in numerous publications and has advanced enough to merit a product which has been marketed by BioRad under the name Biolistic PDS. The use of this and similar systems are described in U.S. Pat. Nos. 4,945,050; 5,015,580; and 5,120,657 and international patent applications WO 95/29703 and WO 93/17706. An improvement upon the particle mediated delivery was made by Palsson, as disclosed in U.S. Pat. No. 5,534,423. The Palsson method includes loading a vector and the cells to be transformed into a centrifuge apparatus and spinning it to bring the vectors into contact with the cells. A spinnable disk and an electrolytic system are also envisioned.